Semiconductor structures including liners comprising alucone and related methods

ABSTRACT

A semiconductor device including stacked structures. The stacked structures include at least two chalcogenide materials or alternating dielectric materials and conductive materials. A liner including alucone is formed on sidewalls of the stacked structures. Methods of forming the semiconductor device are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is related to co-pending U.S. patent applicationSer. No. 14/189,265, filed Feb. 25, 2014 and entitled CROSS-POINT MEMORYAND METHOD FOR FABRICATION OF SAME, and to U.S. patent application Ser.No. 14/189,490, filed Feb. 25, 2014 and entitled CROSS-POINT MEMORY ANDMETHODS FOR FABRICATION OF SAME, the disclosure of each of which ishereby incorporated herein it its entirety by this reference.

FIELD

Embodiments disclosed herein relate to semiconductor devices includingmemory cells having liner materials and methods of forming such devices.More specifically, embodiments disclosed herein relate to structures forincreasing memory density and methods of forming such structures.

BACKGROUND

Due to rapid growth in use and applications of digital informationtechnology, there are demands to continuingly increase the memorydensity of memory devices while maintaining, if not reducing, the sizeof the devices. Three-dimensional (3D) structures have been investigatedfor increasing the memory density of a device. For example, 3Dcross-point memory cells and 3D-NAND cells have been investigated asdevices with increased capacity and smaller critical dimensions.Typically, these 3D structures include stacks of memory cells that mayinclude phase change materials, switching diodes, charge storagestructures (e.g., floating gates, charge traps, tunneling dielectrics),a stack of alternating control gates and dielectric materials, andcharge blocking materials between the charge storage structures andadjacent control gates.

Fabrication of conventional semiconductor devices often requirescreating high aspect ratio openings in a stack of alternating materialson a substrate. Frequently, materials that are highly sensitive todownstream processing conditions are used as part of the stackstructures. For example, stacks in 3D memory arrays may comprisematerials such as chalcogenides, carbon containing electrodes, or othersensitive materials that may be damaged at higher temperatures usedduring conventional semiconductor fabrication processes or may reactwith etchants used during downstream processing. Aluminum oxide has beenused as a liner material to protect the sensitive materials of the stackstructures. However, aluminum oxide may resputter and redeposit onsurfaces of a semiconductor structure during etching. As the aluminumoxide resputters, it may undesirably form in bottom portions or cornersof trench structures or undesirably redeposit on other portions of thesemiconductor structure. Additionally, removing the aluminum oxidewithout damaging the sensitive materials of the stack structures hasproven to be difficult. Aluminum oxide exhibits high dry etch resistanceto CF_(x) based dry etch chemistries and O₂-plasma based carbon etchchemistries.

In addition, as the number of materials in the stacks increase, thedepth and aspect ratio (i.e., the ratio of width to depth) of trencheslocated between adjacent stack structures increases. It is important toconstrain the critical dimension of the structure as the trenches areformed. Therefore, it would be desirable to form high aspect ratiotrenches between stack structures in a device having a 3D architecturewithout increasing the critical dimension of the structure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A through FIG. 1C are simplified cross-sectional views showing analucone containing liner according to some embodiments of the presentdisclosure;

FIG. 2A through FIG. 2F are simplified cross-sectional views of a 3Dsemiconductor structure according to some embodiments of the presentdisclosure, the semiconductor structure including a liner at variousstages of processing; and

FIG. 3A through FIG. 3G are simplified cross-sectional views of another3D semiconductor structure according to some embodiments of the presentdisclosure, the semiconductor structure including a liner at variousstages of processing.

DETAILED DESCRIPTION

The illustrations included herewith are not meant to be actual views ofany particular systems or memory structures, but are merely idealizedrepresentations that are employed to describe embodiments describedherein. Elements and features common between figures may retain the samenumerical designation except that, for ease of following thedescription, for the most part, reference numerals begin with the numberof the drawing on which the elements are introduced or most fullydiscussed.

The following description provides specific details, such as materialtypes, material thicknesses, and processing conditions in order toprovide a thorough description of embodiments described herein. However,a person of ordinary skill in the art will understand that theembodiments disclosed herein may be practiced without employing thesespecific details. Indeed, the embodiments may be practiced inconjunction with conventional fabrication techniques employed in thesemiconductor industry. In addition, the description provided hereindoes not form a complete process flow for manufacturing 3D semiconductorstructures, and the structures described below do not form a completesemiconductor device. Only those process acts and structures necessaryto understand the embodiments described herein are described in detailbelow. Additional acts to form a complete semiconductor device includingthe structures described herein may be performed by conventionaltechniques.

In some embodiments disclosed herein, a liner formed on sidewalls ofstacks may prevent undesired etching or damage to materials comprisingthe stacks. The liner is formed from an aluminum-containing material,such as alucone. The liner may passivate the sidewalls of the stacks andmay be formed during formation of the stacks. The aluminum-containingmaterial may exhibit good adhesion to the materials of the stack, suchas carbon materials, phase change materials, or electrode materials. Inaddition, the aluminum-containing material may be substantiallyconformally formed over the materials of the stack. Thealuminum-containing material may also be formed at a low temperature,decreasing the potential of heat damage to the materials of the stack.Although the aluminum-containing material of the liner is formed at alow temperature, the aluminum-containing material is, nevertheless,easily removed selective to materials of the stack.

In some embodiments, the liner is formed on a first portion of sidewallsof the stacks after the stacks are only partially formed. After formingthe partial liner, bottom portions of the liner may be removed and thestack may be further processed. In other embodiments, the liner isformed on sidewalls of the completed stacks and may remain in the finalstructure. The liner may function as a seal around the materials of thestack, preventing intermixing or migration of the stack materials. Theliner material may, further, be oxidized to densify the liner.

Thus, the liner material may be formed over portions of a stack or overan entire stack structure. The liner may be beneficial in structureswith a high aspect ratio and may be useful in protecting underlyingreactive materials such as chalcogenides or other temperature sensitivematerials. The liner may seal portions of the stack and may preventmigration of one material of the stack into another material of thestack.

According to embodiments disclosed herein, the liner may be formedwithin trenches formed in between adjacent stacks. The stacks may becomprised of various materials, depending on the desired function of thefinal device. For example, in 3D cross-point memory structures, thestacks may include various chalcogenide materials, electrode materials,and phase change materials. In 3D-NAND structures, the stacks maycomprise alternating conductive materials and dielectric materials.

Referring to FIG. 1A, a liner 110 is formed over a stack 105 ofmaterials. The materials of the stack 105 are discussed in more detailbelow. The liner 110 may comprise an aluminum-containing organicmaterial, such as alucone. As used herein, the term “alucone” means andincludes a material that contains aluminum atoms, carbon atoms, andoxygen atoms, such as an aluminum alkoxide polymeric material where thealkoxide is methoxide, ethoxide, propoxide, butoxide, pentoxide,hexoxide, or heptoxide. The alucone may be formed from alcoholprecursors and organometallic precursors to form the aluminum alkoxide.The liner 110 may also include an aluminum-containing inorganic materialin addition to the aluminum-containing organic material. In someembodiments, the inorganic material comprises aluminum oxide and theorganic material comprises the alucone, with the ratio of alucone toaluminum oxide selected depending on the desired properties of the liner110. The liner 110 may be homogeneous in its composition, such asincluding 100% alucone or a single ratio of alucone to aluminum oxide.However, the liner 110 may also include a gradient of aluminum oxide inthe alucone. The liner 110 may be formed by atomic layer deposition(ALD) or molecular layer deposition (MLD). In some embodiments, thealucone is formed by MLD of tri-methyl aluminum (TMA) and ethyleneglycol.

While the liner 110 in FIG. 1A is shown as a single material, the liner110 may include at least a first portion 110 a and a second portion 110b as shown in FIG. 1B, with each of the different portions including adifferent composition of the aluminum-containing material. The twoportions may differ in the atoms that account for their respectivecompositions, or may differ in the relative content of the same atoms.Referring to FIG. 1B, the liner 110 may be formed over the stack 105structure. By way of example only, the liner 110 may include a firstportion 110 a including aluminum oxide, and a second portion 110 bincluding alucone. The first portion 110 a comprising aluminum oxide maybe in contact with the materials of the stack 105, enabling the aluconeof the second portion 110 b to adhere to the materials of the stack 105,such as carbon or chalcogenide materials. The second portion 110 b ofthe liner 110 may include aluminum, carbon, and oxygen. In someembodiments, the alucone may optionally include silicon atoms, nitrogenatoms, or combinations thereof.

In some embodiments, the first portion 110 a comprises a seed materialof aluminum oxide and the second portion 110 b comprises the alucone. Inother embodiments, the liner 110 includes a ratio of aluminum oxide toalucone of approximately 1:1. The ratio of aluminum oxide to alucone mayrange from between about 1:1 to about 1:10 such as from between about1:1 and about 1:5. Thus, for each monolayer of aluminum oxide formed, amonolayer of alucone may be formed. In other embodiments, for eachmonolayer of aluminum oxide formed, between about 1 monolayer and about10 monolayers of alucone may be formed, such as between about 1monolayer and about 5 monolayers of alucone. Since the aluminum oxidemay exhibit increased adherence to the stack materials than the aluconematerial, the aluminum oxide may be in direct contact with the stack105. The alucone may be formed over the aluminum oxide portion and mayadhere to the aluminum oxide formed over the stack structure.

In other embodiments, the liner 110 may include a gradient of aluminumoxide and alucone. For example, the liner 110 may include an aluminumoxide material in direct contact with the stack 105. The concentrationof alucone may increase from approximately zero percent at a surfaceproximal to the stack 105 to about one-hundred percent at an outersurface of the liner 110 (i.e., distal to the stack 105). Thus, theconcentration of aluminum oxide may be approximately one-hundred percentnear the surface of the stack 105 and may decrease to approximately zeropercent at an outer surface of the liner 110.

Referring to FIG. 1C, the liner 110 may comprise different portions withdiffering concentrations of alucone and aluminum oxide. For example, afirst portion 110 a of the liner 110 may be in contact with the stack105 and may comprise an aluminum oxide material. The first portion 110 amay comprise between about one monolayer and about ten monolayers ofaluminum oxide. A second portion 110 b may be formed over the firstportion 110 a and include an alucone material. The second portion 110 bmay include between about ten percent and about seventy percent aluconesuch as between about ten percent alucone and about thirty percentalucone. A third portion 110 c may be formed over the second portion 110b and may have a higher alucone content than the second portion 110 b.The third portion 110 c may comprise between about fifty percent aluconeto about one hundred percent alucone, such as between about fiftypercent alucone and about seventy percent alucone, between about seventypercent alucone and about ninety percent alucone, or between aboutninety percent alucone and about one-hundred percent alucone. The liner110 may have the advantage of good adhesion to the stack structure whilealso exhibiting favorable etching characteristics.

In other embodiments, the liner 110 may comprise only (i.e., consistessentially of or consist of) an alucone material. The alucone materialmay be formed directly in contact with the stack 105.

The aluminum oxide portion of the liner 110, if present, may be formedby atomic layer deposition, chemical vapor deposition (CVD), plasmaenhanced chemical vapor deposition (PECVD), or other deposition method.In some embodiments, the aluminum oxide is formed by atomic layerdeposition. The aluminum oxide may be formed by pulsing aluminumprecursors and oxygen containing precursors sequentially. Non-limitingexamples of aluminum precursors include tris(diethylamino) aluminum(TDEAA), alkyl aluminum precursors such as tri-methyl aluminum (TMA),aluminum alkoxides such as aluminum isopropoxide (AIP), aluminumtri-sec-butoxide (ATSB), aluminum ethoxide, dimethylaluminumhydride(DMAH), aluminum tris(2,2,6,6-tetramethyl-3,5-heptanedionate),triisobutylaluminum (TIBA), tris(dimethylamido)aluminum(III), orcombinations thereof. Oxygen containing precursors may include oxygen(O₂), ozone (O₃), water, or combinations thereof. In some embodimentsthe aluminum precursor is TMA and the oxygen containing precursor iswater.

The alucone portion of the liner 110 may be formed by MLD or by ALD. Thealucone material may be deposited in the same deposition chamber and atsimilar process conditions as the deposition of the aluminum oxidematerial, if present. For example, the alucone material may be formed ata temperature similar to the temperature at which the aluminum oxide isformed. By way of non-limiting example, the alucone material and thealuminum oxide may be formed at a temperature of between about 85° C.and about 175° C., such as between about 85° C. and about 135° C., orbetween about 135° C. and about 175° C. In some embodiments, the aluconeand the aluminum oxide may be deposited at a temperature ofapproximately 175° C.

The alucone material may be formed using the same aluminum precursor asthe aluminum oxide portion. The organic portion of the alucone materialmay be formed from a precursor including at least one hydroxyl group andcarbon, such as a monofunctional or polyfunctional alcohol. The organicprecursor may be pulsed after the aluminum precursor. Thus, the aluconeportion of the liner material may be formed from an aluminum containingprecursor and a carbon containing precursor. The carbon containingprecursor may include ethylene glycol, 1,3-propylene glycol, glycerol(glycerin), other alcohols, or combinations thereof. In someembodiments, the alucone is formed by pulsing TMA with ethylene glycol.The resulting material may comprise an Al:OCH₂CH₂—O material. Each cycleof the aluminum containing precursor and the carbon containing precursormay form between about 1 Å and about 5 Å of the alucone material.

The alucone material may have a lower density and lower hardness thanthe aluminum oxide material. By incorporating alucone into the aluminumoxide material, the density and the hardness of the liner may be tunablecompared to the density and the hardness of the aluminum oxide material.The density and hardness of the alucone material may be increased ordecreased by, respectively, decreasing or increasing the carbon contentof the carbon-containing precursor. Thus, in some embodiments, thealucone material may be formed with precursors in addition to ordifferent from ethylene glycol. For example, rather than pulsingethylene glycol, other carbon containing alcohols, such as 1,3-propyleneglycol, glycerol (glycerin), 1,4-butanediol, glycols with more carbonatoms, or combinations thereof, may be used. By way of non-limitingexample, pulsing 1,3-propylene glycol rather than ethylene glycol mayincrease the carbon content of the alucone material and may decrease thedensity of the alucone. In some embodiments, the carbon-containingprecursor includes ethylene glycol and a different alcohol with a highercarbon content than ethylene glycol, such as 1,3-propylene glycol.

Optionally, the liner 110 may be modified by altering functional groupsin the carbon containing precursor. By changing the functional group inthe carbon containing precursor from a methyl constituent to an aminefunctional group, the composition of the liner 110 may be modified. Forexample, a hetero-bifunctional molecule such as ethanolamine may be usedas the carbon containing precursor. Maleic anhydride or other cyclicanhydrides may be reacted with the amine groups from the ethanolamine toform exposed hydroxyl groups that may be reacted with the aluminumprecursor in the next pulse of aluminum precursor. In other embodiments,the carbon-containing precursor may include other functional groups suchas amino alcohols. Suitable amino alcohols may include methanolamine,propanolamine, a butanolamine, or combinations thereof. Alcohols withother functional groups may also be pulsed to alter the composition ofthe alucone material. For example, the modified precursor may be usedwith the carbon containing precursor such that the organic precursorincludes a portion of ethylene glycol, 1,3-propylene glycol, glycerol,other alcohols and a portion of the modified precursor, such asmethylamine.

Alternatively or additionally, the functional groups may be modifiedafter deposition to alter a surface of the alucone material. In someembodiments, the functional group may be modified with a surfactant,such as a hydrophobic molecule or other wetting agents. The surfactantsmay help reduce toppling of stack structures exhibiting a high aspectratio during subsequent processing steps. Surfactants, alcohols,solvents, or other wetting agents may also be used to align moleculesduring deposition of a seed material. In some embodiments, a precursorcontaining the surfactant may be added to the MLD recipe during the lastMLD cycles. The surfactant may thus be formed on exposed surfaces of theliner 110.

The surfactant may include a cationic surfactant, a nonionic surfactantor combinations thereof. Non-limiting examples of cationic surfactantsinclude quaternary cations, such as lauryl trimethylammonium bromide.Non-limiting examples of nonionic surfactants include polyoxyetheyleneglycol alkyl ethers and polyoxypropylene glycol alkyl ethers. In someembodiments, one or more cationic surfactants and one or more nonionicsurfactants are added to the precursor recipe.

The liner 110 may optionally comprise a portion including at least oneof silicon atoms and nitrogen atoms. The carbon containing precursorsmay be selected to alter the composition of the alucone containing filmto include at least one of silicon atoms and nitrogen atoms. By way ofnon-limiting example, the alucone material may include nitrogen by usinga nitrogen precursor, such as ammonia, in the deposition process. Thealucone material may include silicon by using a silicon precursor duringthe deposition process. Non-limiting examples of silicon precursorsinclude silicon alkoxides such as TEOS, silicon alkaminates such astris(dimethylamino)silane (3DMAS), silicon alkylates, silane, disilane,trisilane, and trisilylamine (TSA). Precursors including both siliconand nitrogen may also be used including, but not limited to, silazane,disilazane, trisilazane, cyclosilazanes, or combinations thereof. Eachof the silicon content and the nitrogen content of the alucone materialmay each comprise from between about zero atomic percent (0 at %) andabout thirty atomic percent (30 at %) of the alucone composition, suchas between about zero atomic percent (0 at %) and about ten atomicpercent (10 at %), between about ten atomic percent (10 at %) and abouttwenty atomic percent (20 at %), or between about twenty atomic percent(20 at %) and about thirty atomic percent (30 at %).

In some embodiments, the liner 110 may, optionally, be exposed to anoxygen source to oxidize and densify the alucone. For example, thealucone in the liner 110 may be oxidized to cross-link the organiccomponents or to replace the organic components with oxygen, convertingthe alucone to an aluminum oxide or a carbon-doped aluminum oxide, whichhave a higher density than the alucone material. Suitable oxidants mayinclude an oxygen plasma, ozone, water, nitrous oxide (N₂O), orcombinations thereof. For example, the alucone may be oxidized by directpartial oxidation, ALD type H₂O or O₂ exposure, or combinations thereof.

The alucone and the aluminum oxide of the liner 110 may exhibitdifferent etch characteristics due to their different densities. Thealucone may be removed with dry plasma etchants, whereas the aluminumoxide exhibits a resistance to dry plasma etching. Suitable dry etchantsfor removing the alucone of the liner 110 may include a chloride basedor a boron trichloride (BCl₃) based dry etch chemistry with ionbombardment. The dry etch process may be suitable for removing thealucone in a vertical direction, such as at the bottom of trenches inbetween adjacent stack structures.

The alucone may also be removed with a semi-aqueous or a solvent wetchemistry including an organic acid or an organic base. The solvent mayinclude dimethyl sulfoxide (DMSO), n-methyl-2-pyrrolidone (NMP),monoethanolamine (MEA), or combinations thereof. The solvent may alsoinclude ethylenediaminetetraacetic acid (EDTA), acetic acid, ammoniumhydroxide, or combinations thereof.

The aluminum oxide may be removed with an aqueous solution comprising aninorganic acid or inorganic base. The solution may include hydrofluoricacid (HF), hydrochloric acid (HCl), phosphoric acid, sulfuric acid, orcombinations thereof. Post etch residues may be removed by cleaning withsolutions comprising acetic acid, citric acid, dilute NH₄OH, orcombinations thereof. After cleaning, a portion of the underlyingaluminum oxide may remain.

Thus, the etchability of the liner 110 may be tuned by altering theamount of the alucone material relative to the amount of the aluminumoxide material to provide favorable etch characteristics. In someembodiments, the alucone and aluminum oxide may be removed with asolvent containing both inorganic acids or bases and organic acids orbases.

The liner 110 comprising the alucone may be more easily removed than aliner material comprising only aluminum oxide. For example, the liner110 including the alucone material may be removed without damagingsurrounding materials, such as materials comprising the stack 105structures. By way of non-limiting example, the alucone containing linermay be etched with a dry plasma etch or with a semi-aqueous based orsolvent based chemistry that may not damage the underlying materials. Incontrast, the wet etching chemistries such as HF, HCl, phosphoric acid,or sulfuric acid solutions, used to remove aluminum oxide materials maydamage underlying materials. Thus, the alucone containing liner may beremoved without using the aggressive etch chemistries needed to removealuminum oxide.

The liner 110 comprising the alucone may be more easily removed (i.e.,punched through) during removal acts than a liner comprising ahomogeneous aluminum oxide material. For example, the alucone may bemore easily etched or punched through with a dry etch chemistry, such asa dry plasma etch, than an aluminum oxide. It is believed that in a dryetch chemistry relying on long-projectile ion bombardment, the lessdense alucone is more easily removed than the more dense aluminum oxide.Thus, by replacing at least a portion of the aluminum oxide withalucone, the liner 110 may be more easily removed with dry etchants thanan aluminum oxide. As plasma etching may be configured to removematerials in a direction perpendicular to the plasma source, plasmaetching may be suitable to remove the liner 110 from horizontal portionsof the structure, such as from a bottom surface of trenches in betweenadjacent stack structures.

The alucone containing liner may also be advantageous over an aluminumoxide liner because the liner 110 comprising alucone may be less proneto resputtering during etching.

The liner materials may be used in various semiconductor devices toprotect various materials such as phase change materials, chalcogenides,carbon materials, or other materials during processing. For example, theliner materials may be used in 3D structures such as 3D cross-pointmemory structures or in 3D-NAND structures. The aluminum-containingmaterial of the liner may be removed before formation of the completed3D structures or may remain in the 3D structures.

Referring to FIG. 2A, a 3D cross-point memory structure 200 is shown atan intermediate processing stage. The structure 200 may include variousmaterials formed over a substrate 220. The substrate 220 may be a basematerial or construction upon which additional materials are formed. Thesubstrate 220 may be a semiconductor substrate, a base semiconductorlayer on a supporting structure, a metal electrode or a semiconductorsubstrate having one or more layers, structures or regions formedthereon. The substrate 220 may be a conventional silicon substrate orother bulk substrate comprising a layer of semiconductive material. Asused herein, the term “bulk substrate” means and includes not onlysilicon wafers, but also silicon-on-insulator (“SOI”) substrates, suchas silicon-on-sapphire (“SOS”) substrates and silicon-on-glass (“SOG”)substrates, epitaxial layers of silicon on a base semiconductorfoundation, and other semiconductor or optoelectronic materials, such assilicon-germanium, germanium, gallium arsenide, gallium nitride, andindium phosphide. The substrate may be doped or undoped.

The structure 200 may include a conductive material 230 formed over thesubstrate 220. A bottom electrode material 240 may be formed over theconductive material 230. A switching diode material 250 may be formedover the bottom electrode material 240. A middle electrode material 260may be formed over the switching diode material 250. A phase changematerial 270 may be formed over the middle electrode 260. A topelectrode material 280 may be formed over the phase change material 270and a hard mask material 290 may be formed over the top electrodematerial 280. The hard mask material 290 may comprise a nitride materialsuch as a silicon nitride. The materials of the structure 200 may beformed on the substrate 220 by conventional techniques, which are notdescribed in detail herein.

The conductive material 230 may comprise any conductive materialincluding, but not limited to, tungsten, aluminum, copper, titanium,tantalum, platinum, alloys thereof, heavily doped semiconductormaterial, a conductive silicide, a conductive nitride, a conductivecarbide, or combinations thereof. In some embodiments, the conductivematerial 230 is tungsten.

The bottom electrode material 240, the middle electrode material 260,and the top electrode material 280 may be formed from the same ordifferent materials. The electrode materials 240, 260, 280 may be formedfrom a conductive material such as tungsten, platinum, palladium,tantalum, nickel, titanium nitride (TiN), tantalum nitride (TaN),tungsten nitride (WN), polysilicon, a metal silicide, or a carbonmaterial. In some embodiments, the bottom electrode material 240, middleelectrode material 260, and the top electrode material 280 are formedfrom a carbon material and comprise carbon electrodes.

Each of the switching diode material 250 and the phase change material270 may comprise a chalcogenide material, such as a chalcogenide-metalion glass, a chalcogenide glass, or other materials. The chalcogenidematerial may include sulfur, selenium, tellurium, germanium, antimony,or combinations thereof. The chalcogenide material may be doped orundoped or may have metal ions mixed therein. By way of non-limitingexample, suitable chalcogenide alloys may include alloys includingindium, selenium, tellurium, antimony, arsenic, bismuth, germanium,oxygen, tin, or combinations thereof. The switching diode material 250and the phase change material 270 may include chalcogenide materialshaving the same composition or different compositions. In someembodiments, the switching diode material 250 and the phase changematerial 270 comprise different chalcogenide materials.

Referring to FIG. 2B, partial stacks 205′ may be formed in structure200. By way of non-limiting example, a portion of hard mask material290, top electrode material 280, and phase change material 270 may beremoved to expose a portion of the middle electrode material 260 andform the partial stacks 205′. The desired portion of the hard maskmaterial 290 may be removed through a mask or reticle (not shown) byconventional techniques, which are not described in detail herein. Thepatterned hard mask material 290 may be used as a mask to remove theunderlying portions of the top electrode material 280 and phase changematerial 270. The partial stacks 205′ may be formed by an isotropic etchprocess, such as dry plasma etching or reactive ion etching. Adjacentpartial stacks 205′ may be separated from one another by a distance ofbetween about 20 nm and about 60 nm, such as between about 20 nm andabout 40 nm, or between about 40 nm and about 60 nm. In one embodiment,the adjacent partial stacks 205′ are separated by about 40 nm. Althougha distance between adjacent partial stacks 205′ shown in FIG. 2B appearsapproximately equal to a height of the partial stacks 205′, in reality,the height of the partial stacks 205′ may be much greater than thedistance between the partial stacks 205′.

A partial liner 225 may be substantially conformally formed over thepartial stacks 205′. The partial liner 225 may be comprised of aluconeand, optionally aluminum oxide, as described above with reference toFIG. 1A through FIG. 1C. By way of example, the partial liner 225 may beformed of alucone, a gradient of alucone and aluminum oxide, or a seedmaterial of aluminum oxide over which the alucone is formed. If thepartial liner 225 includes the seed material of aluminum oxide, thealuminum oxide may be in contact with the partial stacks 205′. Forexample, the aluminum oxide portion may be in contact with the topelectrode material 280, the phase change material 270, and otherportions of the partial stacks 205′, with the alucone portion overlyingthe aluminum oxide portion. The partial liner 225 may contact sidewallsof the partial stacks 205′, such as sidewalls of the hard mask material290, the top electrode material 280, and the phase change material 270.The aluminum oxide portion of the partial liner 225 may be formed byatomic layer deposition and the alucone portion of the partial liner 225may be formed by molecular layer deposition as described above. Althoughthe partial liner 225 is shown in FIG. 2B as being formed over themiddle electrode material 260 at the bottom of trench 215, the partialliner 225 may be formed on any portion of the partial stacks 205′,depending on where the partial etch is terminated.

The partial liner 225 may have a thickness as low as about 5 Å or thepartial liner 225 may completely fill the trenches 215. In someembodiments, the partial liner 225 has a thickness ranging from betweenabout 5 Å and about 30 Å. For example, the partial liner 225 may have athickness of between about 5 Å and about 10 Å, between about 10 Å andabout 20 Å, or between about 20 Å and about 30 Å. The partial liner 225may be formed by conducting one or more ALD cycles, one or more MLDcycles, or combinations thereof. For example, the partial liner 225 maybe formed by performing one MLD cycle. In some embodiments, sufficientALD and MLD cycles may be performed to completely fill the trenches 215with the partial liner 225.

Referring to FIG. 2C, the partial liner 225 may be removed from a tophorizontal portion of the partial stacks 205′ and from a bottomhorizontal portion of the trenches 215. For example, the partial liner225 may be removed from over the hard mask material 290 and from asurface of the middle electrode material 260. The partial liner 225 mayremain on sidewalls of the partial stacks 205′ and may protect the topelectrode material 280 and phase change material 270. These portions ofthe partial liner 225 may be removed by a dry plasma etch. Suitableetchants may include a chlorine (Cl₂) based dry etch chemistry with ionbombardment, a boron trichloride (BCl₃) based dry etch chemistry withion bombardment, or combinations thereof. Thus, these portions of thepartial liner 225 may be removed without using aggressive wet etchchemistries that may damage the partial stacks 205′, sidewalls of whichare protected by the remaining portions of the partial liner 225. Theportions of the partial liner 225 on sidewalls of the partial stacks205′ may remain after the plasma dry etch process and may protect thepartial stacks 205′ during subsequent processing.

Referring to FIG. 2D, the depth of the trenches 215 may be increased byremoving exposed portions of the underlying materials of the partialstacks 205′, thereby forming stacks 205. The exposed portions of themiddle electrode material 260, the switching diode material 250, thebottom electrode material 240, and the conductive material 230 may beremoved while the partial liner 225 remains on the sidewalls of the topelectrode material 280 and phase change material 270. By way ofnon-limiting example, the portions of the middle electrode material 260and the bottom electrode material 240 may be removed with an oxygenbased plasma etch. The switching diode material 250 may be removed witha gas mixture comprising H₂, CH₄, and O₂. The conductive material 230may be removed with a sulfur hexafluoride (SF₆) etch. Since the hardmask material 290 protects a top surface of the stack 205 and thepartial liner 225 protects the sidewalls of the stack 205 materials, acritical dimension (CD) of the top portion of the stacks 205 (includinghard mask material 290, top electrode material 280, and phase changematerial 270) may be substantially similar to the CD of the bottomportion of the stacks 205. Thus, the partial liner material 225 on thesidewalls of the stack 205 materials prevents the CD of the top portionof the stacks 205 from increasing as the depth of the trenches 215increases (i.e., as a bottom portion of the stacks 205 is formed). Theresulting stacks 205 may have an aspect ratio of between about 10:1 andabout 12:1, although the aspect ratio may be higher or lower dependingon the desired final structure.

In some embodiments, a full liner 210 may be formed over the stacks 205,as shown in FIG. 2E. Referring back to FIG. 2A, portions of thematerials overlying the substrate 220 may be removed to expose a topsurface of the substrate 220. Rather than terminating the etch on themiddle electrode material 260 or another intermediate material, portionsof all the materials overlying the substrate 220 are removed until thetop surface of the substrate 220 is exposed. The full liner 210 may beconformally formed over sidewalls and a top horizontal portion of thestacks 205 as well as the top surface of the substrate 220 in thetrenches 215. The material of the full liner 210 may be substantiallythe same as the material of the partial liner 225. For example, the fullliner 210 may include alucone, alucone and aluminum oxide, a gradient ofalucone, or combinations thereof. In some embodiments, the full liner210 may optionally include silicon atoms and/or nitride atoms asdescribed above with reference to FIG. 1A through FIG. 1C.

The full liner 210 may have a thickness as low as about 5 Å or the fullliner 210 may completely fill the trenches 215. In some embodiments, thefull liner 210 has a thickness ranging from between about 5 Å and about30 Å. For example, the full liner 210 may have a thickness of betweenabout 5 Å and about 10 Å, between about 10 Å and about 20 Å, or betweenabout 20 Å and about 30 Å. The full liner 210 may be formed byconducting one or more ALD cycles, one or more MLD cycles, orcombinations thereof. For example, the full liner 210 may be formed byperforming one MLD cycle. In other embodiments, sufficient ALD and MLDcycles may be performed to completely fill the trenches 215 with thefull liner 210.

In some embodiments, the full liner 210 may be further processed toalter the chemistry of the full liner 210 after it has been deposited.For example, the full liner 210 may be oxidized as previously described,to convert the alucone to aluminum oxide.

Referring to FIG. 2F, the horizontal portions of the full liner 210 maybe removed from a top horizontal portion of the stacks 205 and from abottom horizontal portion of the trenches 215 so that sidewalls of thestacks 205 remain protected by the full liner 210 and a top surface ofthe stack 205 remains protected by the hard mask material 290. By way ofexample only, a dry plasma etch as described above with respect to FIG.2C may remove the full liner 210 from the tops of the stacks 205 andfrom bottom portions of the trenches 215. The trenches 215 betweenadjacent stacks 205 may be filled with a dielectric material 235 such asa silicon dioxide material. Additional process acts may then beconducted to form a complete 3D cross-point memory structure 200 fromthe structure in FIG. 2F. The additional process acts may be formed byconventional techniques, which are not described in detail herein.

Accordingly, a semiconductor device is disclosed. The semiconductordevice comprises stack structures comprising at least two chalcogenidematerials overlying a substrate. A liner comprising alucone is onsidewalls of at least a portion of the stack structures.

A method of forming a semiconductor device is also disclosed. The methodcomprises forming stack structures over a substrate and forming a linercomprising alucone over the stack structures. The liner is removed froma bottom portion of trenches between the stack structures while leavingthe liner on sidewalls of the stack structures.

In other embodiments, the alucone containing liner may be used in a3D-NAND memory structure. Referring to FIG. 3A, a semiconductorstructure 300 is shown that may be further processed to form a 3D-NANDflash memory device. The semiconductor structure 300 includesalternating conductive materials 350 and dielectric materials 340 formedover a substrate 320. The alternating conductive materials 350 anddielectric materials 340 may be formed by conventional techniques. Thesubstrate 320 may include a material similar to substrate 220 describedwith reference to FIG. 2A. The substrate 320 may include doped regionsthat form source and drain regions. In some embodiments, a conductivematerial such as a source or drain may be formed on the substrate 320 orwithin the substrate 320. In some embodiments, a data/sense line (e.g.,bit line, digit line, word line, etc.) (not shown), rather than a sourceor drain may be formed over the substrate 320. The data/sense line maybe formed from doped polysilicon, tungsten silicide, tungsten, or otherconventional materials. A control gate material 330 may be formed overthe substrate 320. An etch stop material (not shown) may be formed overthe control gate material 330. The etch stop material may comprise analuminum oxide material, a silicon nitride material, or otherconventional material selected so that the materials of the stacks 305may be selectively removed without removing the other materials of thesemiconductor structure 300.

The control gate material 330 may comprise a control gate such as aselect source gate (SGS) or a select gate drain (SGD) and may beelectrically coupled to a source or drain region or a data/sense line onthe substrate 320. The control gate material 330 may comprise the sameor different materials than the conductive material 350.

The dielectric material 340 may comprise an insulative material such asa silicon oxide. In some embodiments, the alternating dielectricmaterials 340 comprise silicon dioxide. The conductive material 350 maycomprise any known conductive material. By way of non-limiting example,the alternating conductive materials 350 may comprise n-dopedpolysilicon, p-doped polysilicon, undoped polysilicon, tungsten,aluminum, copper, titanium, tantalum, platinum, alloys thereof,conductive silicides, conductive nitrides, conductive carbides, orcombinations thereof. The formation of the dielectric materials 340 andthe conductive materials 350 may be repeated to form the alternatingmaterials over the substrate 320.

A hard mask 390 may be formed over the 3D-NAND structure 300. The hardmask 390 may be a nitride material such as a silicon nitride. Referringto FIG. 3B, a partial etch may form partial stacks 305′ by removingalternating portions of the conductive material 350 and the dielectricmaterial 340. The portions of the conductive material 350 and thedielectric material 340 may be removed with a single etch act, such asby reactive ion etching, dry plasma etching, an anisotropic dry etchprocess, or other suitable etching method. The partial etch mayterminate on one of the dielectric materials 340 or on one of theconductive materials 350.

Referring to FIG. 3C, a partial liner 325 may be formed over the partialstacks 305′. The partial liner 325 may be conformally formed over thepartial stacks 305′. The partial liner 325 may comprise materials asdescribed above with reference to FIG. 1A through FIG. 1C, and mayinclude alucone, alucone and aluminum oxide, a gradient of alucone, orcombinations thereof. In some embodiments, the partial liner 325 mayoptionally include silicon atoms and/or nitride atoms as described abovewith reference to FIG. 1A through FIG. 1C. By way of non-limitingexample, an aluminum oxide portion of the partial liner 325, if present,may be in contact with the partial stacks 305′.

Referring to FIG. 3D, the partial liner 325 may be removed from bottomportions of the trenches 315. Although not shown, the partial liner 325may be removed from a top horizontal surface of the partial stacks 305′.The partial liner 325 may be removed by a dry plasma etch. The plasmaetch may be as described above with reference to FIG. 2C. For example, adry plasma etch may remove the partial liner 325 from the top horizontalsurfaces of the partial stacks 305′ and the bottom portion of thetrenches 315 without removing the partial liner 325 from sidewalls ofthe trenches 315. Thus, these portions of the partial liner 325 may beremoved without an aggressive wet etch chemistry that may damage theunderlying partial stacks 305′. In some embodiments, the partial liner325 may be oxidized as previously described.

Referring to FIG. 3E, the height of the stacks 305′ may be increased bycontinuing to remove exposed portions of the alternating dielectricmaterials 340 and conductive materials 350, thereby forming stacks 305.By removing exposed portions of the alternating dielectric materials 340and conductive materials 350, the depth of trenches 315 is increased.The alternating portions of the dielectric material 340 and theconductive material 350 may be removed as described above. The partialliner 325 may protect the alternating dielectric materials 340 andconductive materials 350 at upper portions of the stacks 305 from beingdamaged and the distance between adjacent stacks may not be increasedduring the etch. The etch may terminate at the etch stop material (notshown) over the control gate material 330. In other embodiments, theetch may remove at least a portion of the control gate material 330 orat least a portion of the substrate 320 and may terminate on the controlgate material 330 or on the substrate 320.

In some embodiments, a full liner 310 may be formed over the stacks 305,as shown in FIG. 3F. Referring back to FIG. 3A, portions of thematerials overlying the substrate 320 may be removed to expose a topsurface of the substrate 320. Rather than terminating the etch on anintermediate dielectric material 340 or another intermediate material asin FIG. 3B, portions of all the alternating dielectric materials 340 andconductive materials 350 overlying the substrate 320 are removed untilthe top surface of the substrate 320 is exposed, forming stacks 305. Thefull liner 310 may be conformally formed over the stacks 305. The fullliner 310 may contact alternating portions of the dielectric material340 and the conductive material 350, the control gate 330, and a portionof the substrate 320. The full liner 310 may be formed as describedabove with reference to FIG. 1A through FIG. 1C and may include alucone,alucone and aluminum oxide, a gradient of alucone, or combinationsthereof. In some embodiments, the full liner 210 may optionally includesilicon atoms and/or nitride atoms as described above with reference toFIG. 1A through FIG. 1C. In some embodiments, the full liner 310 isoxidized as previously described.

In some embodiments, the full liner 310 or partial liner 325 is removedafter the stacks 305 are formed. In other embodiments, the full liner310 or partial liner 325 remains in the final structure. Referring toFIG. 3G, the full liner 310 may be removed from bottom portions of thetrenches 315. Although not shown, the full liner 310 may also be removedfrom a top horizontal surface of the stacks 305.

Additional processing acts may be performed to complete the 3D-NANDstructure. By way of non-limiting example, a charge trap comprising atunnel dielectric, a charge trapping material, and a charge blockingmaterial may be formed over the full liner 310 or partial liner 325. Thetunnel dielectric may comprise a silicon oxide such as silicon dioxide.A charge trapping material such as a silicon nitride may be formed overthe tunnel dielectric. A charge blocking material such as a siliconoxide may be formed over the charge trapping material. Thus, anoxide-nitride-oxide (ONO) material may be formed over the material ofthe full liner 310. In other embodiments, the charge trap may comprisehigh-k dielectrics such as hafnium oxide, zirconium oxide, aluminumoxide, and low-k dielectrics, or combinations thereof may be formed overthe material of the full liner 310 or partial liner 325.

Accordingly, a semiconductor device is disclosed. The semiconductordevice comprises stack structures comprising alternating dielectricmaterials and conductive materials overlying a substrate. A linercomprising alucone is on sidewalls of the stack structures.

While certain illustrative embodiments have been described in connectionwith the figures, those of ordinary skill in the art will recognize andappreciate that embodiments encompassed by the disclosure are notlimited to those embodiments explicitly shown and described herein.Rather, many additions, deletions, and modifications to the embodimentsdescribed herein may be made without departing from the scope ofembodiments encompassed by the disclosure, such as those hereinafterclaimed, including legal equivalents. In addition, features from onedisclosed embodiment may be combined with features of another disclosedembodiment while still being encompassed within the scope of thedisclosure as contemplated by the inventors.

What is claimed is:
 1. A semiconductor structure, comprising: stackstructures comprising at least two chalcogenide materials overlying asubstrate; and a liner comprising alucone on sidewalls of at least aportion of the stack structures.
 2. The semiconductor structure of claim1, wherein the liner comprises a first portion and a second portion, thefirst portion comprising a lower concentration of alucone than thesecond portion.
 3. The semiconductor structure of claim 1, wherein theliner comprises aluminum oxide and alucone.
 4. The semiconductorstructure of claim 1, wherein the liner comprises a first portioncomprising aluminum oxide in contact with the sidewalls of the stackstructures and a second portion comprising alucone over the firstportion.
 5. The semiconductor structure of claim 1, wherein the linercomprises a gradient of alucone and aluminum oxide, the liner comprisingapproximately zero percent alucone proximal to the sidewalls of thestack structures and approximately one hundred percent alucone distal tothe sidewalls of the stack structures.
 6. The semiconductor structure ofclaim 1, wherein the liner further comprises at least one of silicon ornitrogen.
 7. The semiconductor structure of claim 1, further comprisinga tungsten material overlying the substrate.
 8. The semiconductor deviceof claim 1, wherein at least one of the at least two chalcogenidematerials comprises a switching diode material or a phase changematerial.
 9. The semiconductor device of claim 1, wherein the lineroverlies and contacts the at least two chalcogenide materials.
 10. Thesemiconductor device of claim 1, wherein the stack structures comprise acarbon material, the liner overlying the carbon material.
 11. Asemiconductor device, comprising: stack structures over a substrate; anda liner comprising alucone over sidewalls of the stack structures, theliner comprising a first portion and a second portion, the first portioncomprising a lower concentration of alucone than the second portion. 12.The semiconductor device of claim 11, wherein the first portioncomprises aluminum oxide contacting sidewalls of the stack structuresand the second portion comprises the alucone over the first portion. 13.The semiconductor device of claim 11, wherein the liner has a thicknessof between about 10 Å and about 30 Å.
 14. The semiconductor device ofclaim 11 wherein the alucone further comprises between about 10 atomicpercent and about 20 atomic percent silicon.
 15. The semiconductordevice of claim 11, wherein the liner further comprises aluminum oxide,a ratio of aluminum oxide to alucone ranging from between about 1:1 toabout 1:10.
 16. A method of forming a semiconductor device, the methodcomprising: forming stack structures over a substrate; forming a linercomprising alucone over the stack structures, wherein forming the linercomprises forming a first portion of the liner comprising a lowerconcentration of alucone than a second portion of the liner; andremoving the liner from a bottom portion of trenches between the stackstructures while leaving the liner on sidewalls of the stack structures.17. The method of claim 16, wherein forming stack structures over asubstrate comprises forming stack structures comprising at least twochalcogenide materials over the substrate.
 18. The method of claim 16,wherein forming a liner comprising alucone over the stack structurescomprises conformally forming the first portion comprising an aluminumoxide material on sidewalls of the stack structures and forming thesecond portion comprising alucone over the first portion.
 19. The methodof claim 16, wherein forming a liner comprising alucone over the stackstructures comprises forming the alucone by molecular layer depositionwith TMA and ethylene glycol precursors.
 20. The method of claim 16,further comprising oxidizing the liner comprising alucone.
 21. Themethod of claim 16, wherein removing the liner from a bottom portion oftrenches between the stack structures comprises plasma etching theliner.
 22. The method of claim 16, further comprising extending a depthof the trenches after removing the liner from the bottom portion of thetrenches.
 23. The method of claim 16, further comprising removing theliner from the sidewalls of the stack structures.
 24. The method ofclaim 16, wherein forming a liner comprising alucone over the stackstructures comprises forming the liner comprising alucone and aluminumoxide.